Research On FLRDS-FBG Strain Sensor

Due to the advantages of immunity to light source fluctuation and longer absorption path, cavity ring-down spectroscopy technique has atracted researcher's attention. However, it was limited to be used widely to sensor area because its Stringent requirements for the two reflectors. In recent years, fiber loop ring-down spectroscopy technology was proposed on the basis of cavity ring-down spectroscopy technique. Fiber loop ring-down spectroscopy technology has both advantages of cavity ring-down spectroscopy technique and the fiber, so it is novel fiber sensor technology with huge potential. In the thesis, we put forward a strain sensor based on fiber loop ring-down spectroscopy technology and two FBGs, and then analyzed theoretically and verificated experimentally the sensor. The research contents of the thesis are as follows:(1) Strain sensing scheme based on fiber loop ring-down spectroscopy technology and double FBGs is made and analyzed. The relationship between optical pulse ring-down signal and the length of fiber loop, the pulse width, light path loss,and the sensitivity of photoelectric detector is analyzed; Automatic temperature compensation and the relationship between ring-down time and FBG strain are analyzed.(2) Fiber loop ring-down spectroscopy technology experimental system was set up and the relationship between ring-down spectrum of optical pulse and the system parameters was researched. By controlling the parameters of the ring cavity length,pulse width, coupler ratio, and EDFA, the relationship between ring-down time and fiber loop loss was obtained with the help of Matlab software to seek peaks and process them. In addition, the influence of photoelectric detector position on first pulse energy was studies and the best place of photoelectric detector was given.(3) The relationships of ring-down time of optical pulse versus strain and temperature were investigated experimentally by using two different double FBGs.In addition, automatic temperature compensation was verified by putting the FBG indifferent temperature surroundings.